A typical integrated circuit can have numerous separate voltage supply regimes (or pads), which are further sub-divided into even more voltage supply rails residing inside a single die or multi-die package. Generally, external connections to each regime—but not to individual voltage supply rails—provide physical access to each voltage regime for purposes of obtaining voltage and/or current measurements for the individual regimes. The physical access permits measurement of the voltage and current of each regime with laboratory equipment. However, physical access to each individual voltage rail within a voltage regime is generally not possible under run-time conditions since the voltage rails are encapsulated within the package with no external connections leading to the individual voltage rails themselves. As a result, it is not generally possible to measure the current and voltage of an individual voltage rail except in special circumstances.
In many integrated circuit arrangements, software controls the power consumption of the chip in an attempt to ensure that the power that needs to be consumed to accomplish a particular task is utilized in an efficient manner. As the thermal limits of a package are pushed, it is important to give the software greater capability and flexibility in regulating the power consumption of the chip, in part to ensure more efficient operation of the chip and in part because power consumption is a figure of merit in the marketplace. Where measurements associated with each voltage regime are available, the software can control the operation of the chip to minimize power consumption at a gross level. Thus, where multiple blocks, such as for example a mobile display processor, a memory controller, a graphics processor, a video accelerator, and an AXI bus, are all powered as part of a common voltage regime, a measurement of the voltage and current of that particular regime is really just a composite measurement representing the aggregate contributions from all of these blocks. With more refined measurements for each of the blocks, however, the software can provide much better and more efficient power consumption management for that particular voltage regime and hence for the chip itself.
In addition to run-time considerations, measurement of the voltage and current of voltage regimes is also useful during the software development process, which is a long-delay task. The availability of more refined voltage/current measurements beyond the composite numbers available at the voltage regime level can help in reducing this development time and thereby expedite product introduction into the market.
Possible approaches to obtain more refined measurements at the individual voltage rail level exist, but involve using external measurement equipment that is attached to the chip under consideration at multiple measurement points. In such approaches, an external meter, such as an ammeter, can be attached to the chip under consideration at external test points using multiple clips to obtain individual voltage rail
Accordingly, mechanisms for sensing current and/or voltage in individual voltage rails encapsulated within a package are desirable where the mechanisms are included with the package itself.